Add RELATIVE_ORIENTATION sensor implementation on macOS to //device/generic_sensor

device/generic_sensor/public/cpp/sensor_shared_buffer_reader.h

Index: device/generic_sensor/public/cpp/sensor_shared_buffer_reader.h
diff --git a/device/generic_sensor/public/cpp/sensor_shared_buffer_reader.h b/device/generic_sensor/public/cpp/sensor_shared_buffer_reader.h
new file mode 100644
index 0000000000000000000000000000000000000000..41499c8335c4afc4532d9c08a74c7e2d6fa19318
--- /dev/null
+++ b/device/generic_sensor/public/cpp/sensor_shared_buffer_reader.h
@@ -0,0 +1,34 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef DEVICE_GENERIC_SENSOR_PUBLIC_CPP_SENSOR_SHARED_BUFFER_READER_H_
+#define DEVICE_GENERIC_SENSOR_PUBLIC_CPP_SENSOR_SHARED_BUFFER_READER_H_
+
+#include "base/macros.h"
+#include "device/generic_sensor/public/cpp/generic_sensor_public_export.h"
+
+namespace device {
+
+struct SensorReading;
+struct SensorReadingSharedBuffer;
+
+class DEVICE_GENERIC_SENSOR_PUBLIC_EXPORT SensorSharedBufferReader {

[Mikhail, 2017/06/20 13:50:00]

It's a good idea to export this functionality since it's used in Blink as well,
but IMO it would be better just to add a free function "bool
GetSensorReadingFromBuffer(const SensorReadingSharedBuffer* buffer,
SensorReading* result);" and call it both from Blink and from
PlatformSensor::GetLatestReading() which I proposed above.

[juncai, 2017/06/20 19:50:55]

Done.

+ public:
+  explicit SensorSharedBufferReader(const SensorReadingSharedBuffer* buffer);
+  ~SensorSharedBufferReader();
+
+  // Get sensor reading from shared buffer.
+  bool GetSensorReading(SensorReading* result);
+
+ private:
+  bool TryReadFromBuffer(SensorReading* result);
+
+  const SensorReadingSharedBuffer* buffer_;
+
+  DISALLOW_COPY_AND_ASSIGN(SensorSharedBufferReader);
+};
+
+}  // namespace device
+
+#endif  // DEVICE_GENERIC_SENSOR_PUBLIC_CPP_SENSOR_SHARED_BUFFER_READER_H_